In the Venetian lagoon the seaweed proliferation had reached such a level to cause serious problems to the entire ecosystem. Before planning the intervention, Ecolmare, in cooperation with universities and the National Research Center (CNR) carried out an accurate research on seaweed and their geomorphological conformation. Ecolmare's research located a 23 square kilometers area with a high algae concentration, which conveniently treated, has permitted the ecological rebalance of the entire lagoon. While the upper and middle coasts of the Adriatic waters were invaded by a mucilage overproduction, the Venetian lagoon was hit by similar phenomena: macroalgal eutrophication. The most common species are Ulva Lactuga and, in smaller proportion, Enteromorpha and Gracilaria, considered till now a very poor weed. The Ecolmare's laboratory spent energies and resources to study the Ulva's behavior, which has been treated in various ways. This overproduction, eased by the high radiant energy and by the abundance of the lagoon ecosystem created a lack of oxygen which caused the death of fish and invertebrates, while larval forms resistant to the lack of oxygen have become quickly dominant. The causes of the phenomena are to be searched in the polluting elements reaching the lagoon.